linux-bcache.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Coly Li <colyli@suse.de>
To: linux-bcache@vger.kernel.org
Cc: linux-block@vger.kernel.org, Coly Li <colyli@suse.de>
Subject: [PATCH] bcache: reserve never used bits from bkey.high
Date: Thu, 23 Sep 2021 14:19:13 +0800	[thread overview]
Message-ID: <20210923061913.25421-1-colyli@suse.de> (raw)

There sre 3 bits in member high of struct bkey are never used, and no
plan to support them in future,
- HEADER_SIZE, start at bit 58, length 2 bits
- KEY_PINNED,  start at bit 55, length 1 bit

No any kernel code, or user space tool references or accesses the three
bits. Therefore it is possible and feasible to reserve the valuable bits
from bkey.high. They can be used in future for other purpose.

Signed-off-by: Coly Li <colyli@suse.de>
---
 include/uapi/linux/bcache.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/uapi/linux/bcache.h b/include/uapi/linux/bcache.h
index cf7399f03b71..97413586195b 100644
--- a/include/uapi/linux/bcache.h
+++ b/include/uapi/linux/bcache.h
@@ -43,9 +43,9 @@ static inline void SET_##name(struct bkey *k, unsigned int i, __u64 v)	\
 #define KEY_MAX_U64S		8
 
 KEY_FIELD(KEY_PTRS,	high, 60, 3)
-KEY_FIELD(HEADER_SIZE,	high, 58, 2)
+KEY_FIELD(__PAD0,	high, 58, 2)
 KEY_FIELD(KEY_CSUM,	high, 56, 2)
-KEY_FIELD(KEY_PINNED,	high, 55, 1)
+KEY_FIELD(__PAD1,	high, 55, 1)
 KEY_FIELD(KEY_DIRTY,	high, 36, 1)
 
 KEY_FIELD(KEY_SIZE,	high, 20, KEY_SIZE_BITS)
-- 
2.31.1


                 reply	other threads:[~2021-09-23  6:19 UTC|newest]

Thread overview: [no followups] expand[flat|nested]  mbox.gz  Atom feed

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20210923061913.25421-1-colyli@suse.de \
    --to=colyli@suse.de \
    --cc=linux-bcache@vger.kernel.org \
    --cc=linux-block@vger.kernel.org \
    --subject='Re: [PATCH] bcache: reserve never used bits from bkey.high' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).